Over the last few years, the demand for high-speed communication networks has increased dramatically. In many situations, communication networks are implemented with electrical interconnections. As desired levels of bandwidth and transmission speed for communication networks increase, it will become more and more difficult for electrical interconnections to satisfy these levels.
One difficulty associated with electrical interconnections is that they are sensitive to external electromagnetic interference. More specifically, electromagnetic fields that reside in the vicinity of the interconnection lines induce additional currents, which may cause erroneous signaling. This requires proper shielding, which hampers general heat removal.
Another difficulty is that electrical interconnections are subject to excessive inductive coupling, which is referred to as xe2x80x9ccrosstalkxe2x80x9d. To alleviate crosstalk, the electrical interconnections must abide by fundamental rules of circuit routing so that they are set at a distance large enough to prevent neighboring signals from having any adverse effect on each other, which would reduce network performance.
Optical interconnections offer a solution to the difficulties affecting conventional electrical interconnections. For example, optical interconnections are not as susceptible to inductive or even capacitive coupling effects as electrical interconnections. In addition, optical interconnections offer increased bandwidth and substantial avoidance of electromagnetic interference. These potential advantages of optics become more important as the transmission rates increase.
Many communications network feature electronic switching devices to arbitrate the flow of information over the optical interconnections. Conventional electronic switching devices for optical signals are designed to include a hybrid optical-electrical semiconductor circuit employing photo detectors, electrical switches, optical modulator or lasers. The incoming optical signals are converted to electrical signals, which are amplified and switched for driving the lasers. One disadvantage associated with a conventional electronic switching device is that it provides less than optimal effectiveness in supporting high data transmission rates and bandwidth.
In one embodiment, the present invention relates to an optical cross-connect switching system comprising (1) a switch subsystem, (2) a plurality of removable, input/output (I/O) port modules and (3) a switch control subsystem featuring servo modules. These units collectively operate to provide optical data paths for routing of light signals without conversion from optical to electrical domains and back to optical. Also, the optical cross-connect switching system is scalable because the I/O port modules, servo modules and even features of the switch subsystem may be removed without disruption in system operation.
The switch subsystem features at least two optical switch cores each including a number of optical switches such as micro-machined mirrors. The multiple optical switch cores provide redundancy in the event that optical switches for one of the optical switch cores are damaged or inoperable. These optical switch cores are removable without completely disrupting operation of the of the optical cross-connect switching system.
At each port, a removable I/O port module is configured with a splitter and at least two tap couplers. Normally passive in nature, the splitter is configured to produce at least two bridged light signals from an incoming light signal. The tap couplers are used to produce optical tap signals as well as outgoing light signals that are each routed to different optical switch cores. Configurable with a power level lesser than the outgoing light signals, the optical tap signals provide servo modules information for controlling the switch subsystem and monitoring performance variances in the optical data paths. Moreover, each port of an I/O port module includes an optical switch for selectively routing one of the light signals received from the optical switch cores during output operations.
A servo module includes a servo mirror control module and an optical detector module. The servo mirror control module is configured to adjust an optical path of a light signal from a source to a destination. Thus, the monitoring is not performed in the optical data path. The optical detector module, communicatively and removably coupled to the servo mirror control module, monitors a power level of the light signal to determine whether to adjust the optical path. Moreover, the optical detector module includes a laser to inject a substitute light signal into the optical path. The substitute light signal may be within the same wavelength range as the light signal.
Multiple servo modules are in communication with each other through a servo control module and multiple servo control modules are in communication with each other through network control modules.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying claims and figures.